In semiconductor packaging technologies, the wafer is normally cut along a scribe line at the front surface of the wafer to separate individual chip packages from the wafer. However, in some special packaging technologies, for example, molded wafer level packaging (MWLP), the wafer is required to cut from its backside. However, if the backside of the wafer is sealed by molding materials or covered with non-transparent materials, sawing the wafer from its backside along the scribe line located at the front surface of the wafer becomes a big challenge.
U.S. Pat. No. 6,107,164 discloses a wafer level packaging method, which is shown in FIGS. 1A-1D. As shown in FIG. 1A, a wafer 10 includes semiconductor chips at its front surface and an electrode metal pad 2 connected to electrode bump 4 via a copper interconnection or wire 3. Groove 22 is formed between two adjacent semiconductor chips by cutting the wafer 10 via a blade 21 to a depth deeper than half of the thickness of the wafer 10. The front surface of the wafer 10 and the electrode bump 4 are covered with a layer of resin 23, as shown in FIG. 1B, with the resin 23 fully encapsulating the electrode bump 4. As shown in FIG. 1C, the resin 23 is then ground and polished by a polishing blade 24 until the electrode bump 4 is exposed from the resin 23. As shown in FIG. 1D, the wafer 10 is then ground at its backside until the groove 22 filled with the resin 23 is exposed at the backside of the wafer 10. Individual chip packages are separated by sawing the wafer 10 from its backside through the groove 22 using a dicing blade 26. However, it is preferable that the wafer sawing is performed by cutting through groove 22 at the front surface of the wafer 10 for a better alignment. Furthermore, the cutting groove 22 must be controlled to have a certain depth and the wafer 10 must be controllably thinned to a certain thickness to expose the groove 22. In addition, if the backside of the wafer is covered with molding materials, the groove 22 is thus covered with molding material, as such, the wafer dicing step, cutting the wafer through groove 22 via the dicing blade 26, is more challenging.